Formation of intermetallic and intermetallic-type precursor alloys for subsequent mechanical alloying applications

Abstract

A method for forming intermetallic and intermetallic-type precursor alloys for subsequent mechanical alloying applications. Elemental powders are blended in proportions approximately equal to their respective intermetallic compounds. Heating of the blend results in the formation of intermetallic compounds whereas lack of heating results in intermetallic-type powder without the intermetallic structure. The resultant powder is then blended to form a final alloy. Examples involving aluminum-titanium alloys are discussed.

The embodiments of the invention in which an exclusive property or privilege is claimed as defined as follows: 
     
       1. A method for forming precursor alloys for subsequent mechanical alloying into a final alloy, the precursor alloy including a principal element, and at least one secondary element, the method comprising: (a) blending metallic powders including the principal element and the secondary element in a proportion equivalent to the composition of an intermetallic compound formed by the principal and secondary elements, the percentage of the secondary element in the precursor alloy in excess of the percentage of the secondary element in the final alloy to form a first blend,   (b) mechanically alloying the first blend,   (c) adding an additional quantity of the principal element to the mechanically alloyed first blend to raise the percentage of the principal element to the level of the principal element in the final alloy to form a second blend, and   (d) mechanically alloying the second blend.   
     
     
       2. A method according to claim 1 wherein the first blend is heated prior to mechanically alloying. 
     
     
       3. A method according to claim 1 where the final alloy is an aluminum-base alloy including about 4% titanium. 
     
     
       4. A method according to claim 1 wherein the mechanically alloyed first blend is an intermetallic compound. 
     
     
       5. A method for forming aluminum-base alloys by mechanical alloying techniques, the method comprising: (a) blending aluminum powder and at least one non-aluminum element to form a first blend, the percentage of the non-aluminum element in excess of the percentage of the non-aluminum element in the aluminum-base alloy,   (b) mechanically alloying the first blend,   (c) adding an additional quantity of aluminum powder to the first blend to raise the percentage of the aluminum to that of the aluminum-base alloy to form a second blend, and   (d) mechanically alloying the second blend.   
     
     
       6. A method according to claim 5 wherein the first blend has the composition of the intermetallic compound formed by the elements. 
     
     
       7. A method according to claim 6 wherein the first blend includes about 62.8% aluminum and 37.2% titanium plus impurities and processing aids. 
     
     
       8. A method according to claim 6 wherein the first blend is heated to a temperature below the solidus temperature of the elements included in the first blend to form an intermetallic compound. 
     
     
       9. A method according to claim 5 wherein the aluminum-base alloy includes about 4% titanium.